A shock absorbing system comprising a plastically deformable tube linking the bumper of a vehicle with a fixed element of its structure or chassis, specifically a beam, is known from patent document WO 2009/063275.
The deformable tube is linked to the beam by means of a retaining device adapted to adopt a blocking position in which it prevents the relative movement between the aforementioned deformable tube and the beam, and a releasing position which allows the displacement of the deformable tube in relation to the aforementioned beam.
This retaining device comprises a pyrotechnic actuator controlled by an electric impulse which upon being triggered allows the retaining device to go from adopting the blocking position to adopting the releasing position almost instantaneously.
For the operation of the system, the vehicle is equipped with the sensing means necessary to discern between a collision with a pedestrian and a collision with any other obstacle, and which in the first case generate an electrical signal for activating the pyrotechnic actuator if certain predetermined conditions generally related to other aspects, such as the speed or instantaneous acceleration of the vehicle, are met.
Consequently, if something or someone is hit and the impact meets pre-established conditions, the sensing means generate an electrical signal which triggers the pyrotechnic actuator and therefore the retaining means adopt the releasing position, allowing displacement of the deformable tube in an axial direction and thereby the displacement of the bumper of the vehicle, it being retracted in the direction towards the inside of the vehicle on impact with the pedestrian, for the purpose of reducing the damages caused.
If a collision occurs with any other obstacle and the previously mentioned conditions are not present, the sensing means do not generate any electrical signal and therefore the retaining means, which adopt their blocking position, prevent the relative movement between the deformable tube and the vehicle chassis. Consequently, due to the effect of the impact, the bumper is displaced in a direction towards the inside of the vehicle but in this case the deformable tube is deformed by absorbing part of the energy of the collision.
Patent documents EP 1854676 and FR 2928318 describe systems similar to that described above.
Patent document WO 2004113131 describes an energy absorbing system also applicable to the bumper of a vehicle comprising a deformable tube and tube retaining means to prevent or allow its displacement with respect to a beam if certain conditions are met. Basically, this system differs from the previous ones in the nature of the sensing means and in the pre-established conditions which must be met so that when the vehicle collides the retaining means go from adopting a blocking position to a releasing position.
All the systems described have in common that the deformable tube is provided with a series of perforations intended to cooperate with retaining bodies that are provided in the retaining device. In the blocking position said retaining bodies penetrate or even traverse the deformable tube through its perforations and thus prevent its displacement in the axial direction. Nevertheless, none of these documents describes any mechanical solution for displacing the retaining bodies from their blocking position to their releasing position almost instantaneously.
An absorbing system, the retaining means of which are simple and effective, forming a self-supporting unit with the actuator and are versatile in the sense that they can function with actuators of a distinct nature, is an objective of the present invention.
In addition, a drawback related to perforated deformable tubes is that these perforations alter the mechanical properties of the deformable tube, and the configuration and arrangement of the retaining bodies, generally in the form of pins which extend in a direction perpendicular to the axis of the deformable tube, entails in practice that the retaining stresses are concentrated in very small areas of the deformable tube, and this causes it to break or bend when a collision occurs, when what is desired is for it to be crushed in an axial direction in the form of a bellows to absorb a maximum amount of energy in the event of a collision. A system which improves the energy absorption capacity in the event of a vehicle collision is therefore another objective of the present invention.
A system that is more economical than the known systems is also a secondary objective of the invention.